About 20 years ago, I was teaching some young men and women to install insulation in crawlspaces using the conventional method at the time—batts of unfaced insulation between the floor joists, held in place by wires wedged between the joists. The vents in the crawlspace walls remained. These were unheated spaces.We put plastic sheeting on the soil, mostly to keep from getting dirty and to make it easier to slide around the space. In one of the crawlspaces there was so much ductwork, piping, wires, and so on, that it was nearly impossible to get at the joist spaces. I decided to try something different. We would not insulate the floor joists, but we would insulate the perimeter walls of the crawlspace. We ran the plastic up the sides of the crawlspace and stapled it to the sill plates to keep moisture out of the batts of insulation that we had placed up through the band joist area and stapled to the joists and/or the flooring.We stapled the edges of the insulation backing together to keep the batts tight to each other and let ...